Twisted pair cables allow data to be transferred over a segment with a maximum length of about 100 meters. However, these cables do not always make it possible to guarantee the integrity of data over long distances at high speeds.
Twisted pair cables are rated by category, which means that there are several categories of cable having different transfer characteristics. Cables in Category 1 are traditional telephone cables. Such Category 1 cables allow voice transfer but not data transfer. Cables in Categories 2 through 5e are cables that allow data transfer. These cables are composed of four twisted copper pairs. Category 2 cables allow a maximum speed of 4 Mbps. Category 3 cables allow a maximum speed of 10 Mbps. Category 4 cables allow a maximum speed of 16 Mpbs. Category 5 cables allow a maximum speed of 100 Mbps, and Category 5e cables allow a maximum speed of 1 Gbps. This type of cabling can, for example, be connected to an RJ45-type connector.
Transferring audio and video data between a server, typically a computer, and a client, typically a decoder which can be incorporated into a battery powered LCD panel, in this type of network generally requires the audio and video data to be encoded. This is done using space-time encoding. Space-time encoding fully encodes only part of the images to be transmitted in order to reconstruct a video. Thus, for example, only one image in five may be fully encoded. The images that are not fully encoded are directly referred, for the non-encoded parts, to the identical parts encoded by the previously fully encoded images. Thus, a non-fully encoded image includes only the parts of the image that have changed from the previous images and the addresses of the parts of the image that are unchanged from the previously encoded images. Furthermore, certain types of encoding compress the audio and video data, along with the signaling data that allow these data to be delivered correctly, into a single block.
This compression makes it possible to save on bandwidth use during the transfer. For cables like those described above, this bandwidth savings is not insignificant. The decoding is done by the client. Once this decoding is done, the audio and video are delivered by the client via its own delivery means, for example a battery powered LCD panel comprising a screen and speakers in addition to the decoder.
Thus, one of the standards used today is, for example, H264—more particularly, “H264 transport stream,” also referred to below as H264 TS. H264 TS includes both audio data and video data. In addition, H264 TS includes the signaling data that allow the audio and video data to be synchronized.
However, in order to economize on bandwidth, the data must be compressed as much as possible. This substantial compression makes both encoding and decoding highly complex. In essence, the server must not only perform an image compression but must also perform numerous calculations for determining the addresses and the data to be encoded. Likewise, the client decodes these audio and video data as a result of numerous calculations. For a client like a simple decoder, this complexity makes the decoding chips very complex to produce, given that the decoder performs the decoding at the hardware level. Furthermore, this complexity substantially increases the power consumption of such a device due to the number of calculations that must be performed for the encoding and decoding. This excess power consumption makes it problematic to use certain devices, such as a battery powered LCD panel, in which the power reserves are limited.